Not everything would stay in this planet forever. As we know science moves the nature and we know technology improves society (aka Naturalism). But we will all die one day, and even the physical materials will be broken, Jaded, and even be forgotten. Then what's the use of all these things. I personally believe that afterlife is really meaningful, because I know I will go to God when I die rather than everything dying and being forgotten. [I'm a christian, so it contains a Christian world view :) ].
If "God" exist , why would he feel the need to give a life we can spend gambling our chances and a life of boredom and obedience or eternal damnation? It doesn't make sense , you see. Its quite useless , most of us wouldn't even end up in a heaven and if we do wed be kicked very soon for disagreeing. After all , he kicked out groups of his own angles.